An airplane is propelled by one or more power plants each comprising a turbojet engine housed in a tubular nacelle. Each power plant is attached to the airplane by a pylon generally situated under a wing or at the fuselage.
A nacelle generally has a structure comprising an air inlet upstream of the engine, a central section intended to surround a fan of the turbojet engine, a downstream section housing thrust reversal means and intended to surround the combustion chamber of the turbojet engine, and generally ends in a jet pipe nozzle the outlet of which is situated downstream of the turbojet engine.
The air inlet comprises, on the one hand, an inlet lip designed to optimally funnel toward the turbojet engine the air needed to supply the fan and the internal compressors of the turbojet engine and, on the other hand, a downstream structure to which the lip is attached and which is intended to suitably channel the air toward the blades of the fan. The assembly is attached upstream of a casing of the fan belonging to the upstream section of the nacelle.
In flight, depending on the temperature and moisture conditions, ice may form on the nacelle at the external surface of the air-inlet lip. The presence of ice or frost alters the aerodynamic properties of the air inlet and disrupts the flow of air to the fan.
One solution for defrosting or de-icing the external surface is to prevent ice from forming on this external surface.
Thus, it is known practice to bleed hot air from the turbojet engine compressor and convey it to the air-inlet lip in order to heat the walls. However, such a device entails a system of pipes for carrying the hot air between the turbojet engine and the air inlet, and a system of removing the hot air from the air-inlet lip. This increases the mass of the power plant, and this is not desirable.
Patent EP 1 495 963 proposes applying a resistive heating element to an exterior wall of the air-inlet lip. This technology entails the addition of anti-erosion protection over the top of the de-icing resistive heating element.
A solution such as this has a number of disadvantages. First, the anti-erosion product is ill-suited to the surface finish required of the external wall of the lip. Next, if the air-inlet lip is partially covered, it exhibits a discontinuity which is detrimental to the aerodynamic lines of the air inlet. Finally, such a system contributes to increasing the total thickness of the lip, and this may lead to a downturn in acoustic attenuation performance, this being associated with the thickness of the air-inlet lip.
Also known is a structure for a turbojet engine nacelle air-inlet lip comprising an external skin and an internal skin between which there is an electrical heating element.
A disadvantage of this structure is that the electrical heating element has to be constantly electrically powered to prevent ice from forming on the structure. The disclosure provides a turbojet engine nacelle air-inlet lip assembly that offers effective de-icing and effective defrosting without the risk of damaging the turbojet engine, without increasing the mass of the nacelle, without disrupting the aerodynamic lines or the acoustic attenuation, and which does not require a permanent supply of electrical power.